Dizziness and fainting

Today at church I got really dizzy and started to pass out. It was really warm in there and I went to the bathroom where it was cooler and drank some water and started to feel better. I ate a large meal as soon as I could and felt better for a while, but the dizziness keeps returning. It has me freaked out. It's so bad I'm even scared to drive. Has this happened to anyone else? Is it normal?